1. Technical Field
The present invention relates to the processing of animal hides. More specifically, the present invention relates to methods for preparing animal hides for chrome tanning.
2. Background and Relevant Art
Tanning is the process of transforming an animal hide into leather by treating the hide with chemicals that prevent the hide from decaying and make the hide supple and durable. Commonly, the hide is produced at a slaughterhouse where animals are slaughtered to harvest meat. However, the hide may also be produced at a facility where animals are slaughtered for reasons other than to harvest meat, such as a knackery or tannery. Thus, while the vast majority of leather is made from the hides of cattle, sheep, pigs, and goats, a wide assortment of leather is also produced from the hides of various other animals, such as deer, bison, buffalo, ostrich, kangaroo, crocodile, alligator, snake, eel, and stingray.
Following removal of the hide from an animal carcass, curing is used to prevent decomposition of the hide before the hide is subjected to further tanning processes. Examples of curing include treating the hide with salt or preserving the hide at a cold temperature, such as by packing the hide with ice. Accordingly, curing facilitates the preservation of the hide while it is transported to a tannery.
Once received at a tanning facility, the animal hide is subjected to processes that remove non-leather forming substances, such as hair and fat, from the hide. Such processes, which are generally referred to as beamhouse operations, may include trimming, fleshing, dehairing, liming, bating, deliming, and pickling. Trimming is performed to remove unwanted or unusable portions of the hide. Soaking is used to make the hide soft and flexible by reintroducing into the hide moisture lost in curing. Fleshing facilitates the penetration of chemicals into the hide by removing fat and other substances and may also be used to shape the hide into a uniform thickness. Dehairing removes hair and other non-leather forming substances from the hide by treating the hide with chemicals. Liming is the most common method of dehairing. Thermal, oxidative, and other chemical methods of hair removal are also used for this purpose, as are mechanical processes of dehairing, called scudding. Liming is also employed to swell and break up tissue fibers in the hide, as well as prepare the collagen in the hide for proper tanning. Bating and deliming involves treating the hide with enzymes that remove undesirable components of the tissue of the hide to make the hide soft, stretchable, and flexible. Pickling is used to preserve the hide or prepare the hide for tanning by changing the acidity of the hide.
Following beamhouse operations, the animal hide is tanned using one of two chemical tanning processes: chrome tanning or vegetable tanning. These create a reaction between collagen fibers of the hide and chemical tanning agents. Chrome tanning involves treating the hide with chromium, whereas vegetable tanning involves treating the hide with vegetable tannins. Other tanning agents are also used, such as alum, syntans, formaldehyde, glutaraldehyde, and heavy oils. Once tanning is complete, the tanned hide may be processed further before being made into finished leather. Further processing involves wringing, grading, splitting, and shaving of the tanned hide. Finally, the tanned hide is subjected to retanning, coloring, fatliquoring, and finishing processes that produce finished leather.